The present invention generally relates to a fuel injection type carburetor, and more particularly relates to a fuel injection type carburetor of multi-cylinder internal combustion engines.
In the field of multi-cylinder gasoline internal combustion engines, a fuel injection type carburetor has been already proposed. The proposed carburetor comprises respective fuel injection valves arranged in respective intake manifolds adjacent to intake ports of respective cylinders, so that each fuel injection valve injects a required amount of fuel into the intake port of the corresponding cylinder. With this type of fuel injection carburetor, the amount of fuel to be supplied into each cylinder is advantageously uniform. On the other hand, with this type of carburetor, atomization of fuel to be supplied into the cylinders is not fully attained and a large number of fuel injection valves are required.
In order to solve these problems, another type fuel injection carburetor has been proposed, wherein one fuel injection valve is provided in the collecting portion of an intake manifold, so that fuel injected from the fuel injection valve is distributed to respective cylinders. With this type of fuel injection carburetor, it is advantageous that the fuel injection valve is electronically controlled so that a certain amount of fuel required for one combustion in each combustion chamber is intermittently injected from the fuel injection valve, and the injection fuel is, in turn, supplied into respective combustion chambers. As a result, the amount of fuel to be supplied into respective combustion cylinders is uniform.
With the latter of the above mentioned two types of fuel injection carburetors, however, the position of the fuel injection valve, the direction in which fuel is injected, and the shape of the throttle valve have a large influence on the atomization characteristics of the fuel and the uniformity of the amount of fuel to be supplied into the respectively cylinders.